As a technique for imparting water and oil repellency to the surface at the same time, it has been common to treat an object with an organic solvent solution or an aqueous dispersion of a polymer containing polymerization units of a polymerizable monomer containing a polyfluoroalkyl group (hereinafter, a polyfluoroalkyl group will be referred to as an Rf group) in its molecule (hereinafter, such a monomer will be referred to also as an Rf monomer) or a copolymer of such a polymerizable monomer with additional monomers (hereinafter such a polymer and a copolymer will be referred to also as Rf group-containing polymers).
The development of such water and oil repellency is attributed to formation of “a low energy surface” having a low critical surface tension on the surface of a coating film by surface orientation of Rf groups. It has been considered that in order to develop both water repellency and oil repellency, the orientation of Rf groups on the surface is important, and in order to realize the surface orientation of Rf groups, it is important that the polymer has a melting point attributable to fine crystals derived from Rf groups. For this purpose, an Rf group monomer which forms a homopolymer having a melting point attributable to fine crystals derived from Rf groups (crystallizable Rf group-containing monomer) has been used.
Compositions having a polymer containing polymerization units of such a crystallizable Rf group-containing monomer (hereinafter, referred to also as a crystallizable polymer) as an active component achieve the purpose of developing water and oil repellency at most, and improvements have been made in other practical functions.
For example, durability against e.g. washing, dry cleaning and abrasion has been improved by using a monomer which provides high hardness or a monomer having a crosslinkable reactive group in addition to the crystallizable Rf group-containing monomer, or by blending the resulting copolymer with a polymer capable of forming strong coating films.
Further, investigations for softening the hard hand and lowering the melting point of Rf groups in order to develop the water repellency under low-temperature curing conditions, have been made. For example, it is known to copolymerize a monomer containing a perfluoroalkyl group (hereinafter, a perfluoroalkyl group will be referred to as an RF group) having widely ranging chain lengths with an alkyl group-containing monomer. Further, use of a silicone containing an RF group having widely ranging chain lengths is also known.
For example, a cosmetic composition containing a fluorine type compound and a wax having a specific melting point (for example, JP-A-7-173025), a tetrapolymer comprising an RF group-containing (meth)acrylate, stearyl (meth)acrylate and other two types of monomers as essential components (for example, JP-A-10-237133), a mixture of a fluorine type water and oil repellent with an alcohol containing an RF group having a specific chain length or a perfluoropolyether group-containing alcohol (for example, JP-A-10-81873), and a reaction product of an amino group-containing silicone and an Rf group-containing ester compound (for example, JP-A-8-109580) are known.
Meanwhile, as an example using an Rf group-containing monomer having a limited chain length, an acryl type heptapolymer having RF groups with a specified chain length distribution (for example, JP-A-62-179517) may be mentioned. It contains at least 40% of crystallizable Rf group-containing monomers.
The techniques in this field used in these known art references have improved physical properties from a viewpoint of functions required in addition to water and oil repellency, without impairing the water repellency and oil repellency attributable to Rf groups. However, since an Rf group-containing crystallizable polymer is used as the main component, the following demerits resulting therefrom have not been fundamentally overcome.
In conventional water and oil repellents, in order to impart water and oil repellency, it has been considered essential to use a crystallizable Rf group-containing monomer which has an Rf group capable of forming fine crystals having a high melting point (usually at least 70° C.), among crystallizable Rf group-containing monomers.
However, if a crystallizable Rf group-containing monomer is used, the entire polymer will have high crystallinity attributable thereto, and accordingly, an object coated or treated with such a polymer becomes very hard. For example, intrinsically soft fiber products may lose their soft hand, and since the coating film is hard and brittle, defects such as hand marks and chalk marks formed during handling the object tends to remain on raw fabrics as the finished products.
Further, there has been a demerit that the water and oil repellency is initially high right after the treatment with a water and oil repellent is high, but tends to extremely deteriorate by abrasion during the use or by repeated washings. Namely, a water and oil repellent which can maintain the initial performance stably has been desired. Further, there are problems such as insufficient adhesion of the coating film on the surface and vulnerability to cracks and fractures which deteriorate the quality of the object, and therefore, it has been desired to overcome such problems.
Further, when a crystalline polymer is used as the main component, in order to obtain a uniform coating film having high water and oil repellency, usually, a post-application film formation step comprising melting the polymer at a temperature higher than the melting point of fine crystals and cooling has been essential. However, in the case of fiber products made of materials such as extrafine-denier fibers or modified cross-section fibers, such a high temperature treatment causes problems such as deterioration of color fastness, hard hand or fading, and therefore can lower the quality of treated objects.
Heretofore, in order to solve the problems with crystalline polymers, such techniques for lowering the crystallizability of the polymers and for making the polymers flexible are known. Further, for the purpose of forming a film at a low temperature, such techniques as use of a film coalescing aid and copolymerization of a polymerizable monomer containing a branched alkyl group and having an internal plasticization effect with a crystallizable Rf group-containing monomer are known. However, in such a case, there are problems such as failure to development of water and oil repellency, insufficient coating film strength, inadequate adhesion to the substrate or deterioration of the durability because the crystals derived from Rf groups for development of water and oil repellency are partially destroyed.
Further, there has been a problem that on a surface treated with a water and oil repellent having a crystalline polymer as an active component, the adhesion and the hand are not satisfied at the same time. Namely, even when attempts to impart various functions to the surface of fiber products treated with a water and oil repellent containing a crystalline polymer, such as attachment of a film laminate or a seam tape for imparting waterproofness, and attachment of a coating of a urethane or acrylic resin for imparting moisture permeability and waterproofness, were made. It has been difficult to secure sufficient adhesion because the crystallizable Rf groups impair the adhesion. Use of a copolymer of a crystallizable Rf group-containing monomer and a specific monomer such as vinyl chloride may improve adhesion, but it tends to make the hand of fibers still harder, and thus, the adhesion and the hand have not been satisfied at the same time.
Further, in recent years, as a medium for water and oil repellents, it is required to use a medium, which are friendly to the working and global environments, such as a water-based medium (hereinafter referred to as “aqueous medium”), an alcohol solvent, a petroleum solvent called a weak solvent or a fluorine solvent such as a hydrofluorocarbon having little influence on the ozone layer. However, conventional water and oil repellents having a crystalline polymer as an active component are not friendly to the working and global environments, because they need to use a so-called strong solvent such as an aromatic solvent, a ketone or an ester, a chlorinated solvent or a fluorinated solvent such as a chlorofluorocarbon having a great influence on the ozone layer.
The present inventors studied in detail the mechanism of development of water and oil repellency and found out that practically required functions such as substantial water and oil repellency and durability can be developed by using a polymer containing polymerization units of a specific Rf group monomer which has not been used in the field of water and oil repellent coatings because its homopolymer has no melting point or a low melting point attributable to fine crystals derived from Rf groups and the homopolymer has a glass transition point of at least 20° C., and polymerization units of a monomer having a specific cross-linkable functional group, presumably by virtue of the synergistic effect of acceleration of the surface orientation of the Rf group and fixation of the Rf group.
A water and oil repellent based on this concept can form a coating film at a lower temperature than conventional water and oil repellents. The resulting coating film is flexible and tough, and is excellent in adhesion to a substrate.
Accordingly, water and oil repellency can be imparted to objects without accompanying conventionally problematic quality deterioration due to e.g. hardening of the hand or embrittlement of films. Further, sufficient water and oil repellency can be imparted even if the resulting object is treated at a lower temperature than before. Further, the performance hardly deteriorates even by e.g. abrasion or washing.
Further, such a water an oil repellent shows much better adhesion during lamination or coating than conventional water and oil repellents. Further, the copolymer in the present invention dissolves well in e.g. an alcohol solvent, a weak solvent or an ozone-friendly fluorinated solvent such as hydrofluorocarbon, and therefore a solvent having few environmental and safety problems can be used as a medium.